A Krimpsiekte-like Syndrome in Small Stock Poisoned by Ornithogalum Toxicarium Archer & Archer

INTRODUCTION During the last few years reports have been received from farmers of large numbers of sheep and goats dying of an unknown plant poisoning in the Keetmanshoop district, Namibia. A small bulbous plant, which sprouted soon after good winter rain (>20 mm) and provided the only greenery available on the barren rangeland, was ingested by small stock. Stiffness, lagging behind the rest of the flock, a tucked-in appearance, weakness, recumbency, neck paresis, torticollis, jerky respiration, groaning, dysphagia and occasional mild to moderate diarrhoea in sheep and goats were reported by the stock owners. When stressed, the animals succumbed more rapidly and high mortality was reported. The farmers referred to the syndrome as krimpsiekte. 'Kwylbek' krimpsiekte or 'natbek'


INTRODUCTION
During the last few years reports have been received from farmers of large numbers of sheep and goats dying of an unknown plant poisoning in the Keetmanshoop district, Namibia.A small bulbous plant, which sprouted soon after good winter rain (>20 mm) and provided the only greenery available on the barren rangeland, was ingested by small stock.Stiffness, lagging behind the rest of the flock, a tucked-in appearance, weakness, recumbency, neck paresis, torticollis, jerky respiration, groaning, dysphagia and occasional mild to moderate diarrhoea in sheep and goats were reported by the stock owners.When stressed, the animals succumbed more rapidly and high mortality was reported.The farmers referred to the syndrome as krimpsiekte.
'  reported suspected cardiac glycoside intoxication in small stock in the Karas mountains region of southern Namibia.An estimated 2077 sheep and 759 goats had died, presumably of Ornithogalum nanodes Leighton poisoning.Intoxicated small stock had a tucked-in appearance and exhibited signs of star-gazing, torticollis, abdominal breathing, ruminal stasis, muscle trembling, tremors and tired rapidly when mustered.Diarrhoea was only observed on 1 occasion.Necropsy findings were non-specific and included pulmonary oedema and congestion, and congestion of the liver.
Poisoning of livestock with cardiac glycoside-containing plants is collectively the most important plant poisoning in southern Africa 11 .Chemically, 2 major groups of cardiac glycosides, namely the cardenolides and bufadienolides, are recognised.Poisoning by bufadienolidecontaining plants, which surpasses cardenolide-induced poisonings in importance, may be either acute or chronic 10,11 .Tulp poisoning (induced by various Homeria and Moraea species) and slangkop poisoning (caused by various Urginea species) induce only acute toxicity, as these species contain non-cumulative bufadienolides 10,11 .Acute poisoning is characterised by arrhythmia, runs of tachycardia, heart-block, dyspnoea, posterior paresis, bloat and diarrhoea or constipation 10,11 .
As krimpsiekte has previously not been ascribed to any other plant family or genera, the similarity in the toxicity induced by the incriminated plant and reference to the condition as krimpsiekte by the farmers warranted confirmation.

Plant material
Fresh plant material was collected on the farm Schanzen (27°S, 19°E AB), Keetmanshoop district, for botanical identification and dosing trials to ascertain the toxicity of the unknown plant.Fresh plant specimens from the farm Middelwater (32°05'S, 22°00'E), Beaufort West district were also submitted for botanical identification.

Laboratory trial
Two South African Mutton Merino sheep were housed in individual pens with concrete floors at the Laboratory Animal Facility of the Division of Toxicology at the Onderstepoort Veterinary Institute.The sheep had free access to water and were fed a ration consisting of milled lucerne hay and a maize-based concentrate.During a 2-week adaptation period, clinical examinations and electrocardiographic (ECG) (Electromed, Medical Distributors) recordings were carried out weekly.To facilitate ECG recordings, the sheep were placed in a crate equipped with a neck clamp and the ECG leads (Lead 2) connected.Both sheep were deprived of feed and water on Day (D) -1.On D 0 the sheep were weighed and dosed according to this mass.Once dosing commenced the ECG recordings were performed more regularly (i.e.2-6 times per day).The plant material was blended and dosed to the sheep according to the regimen indicated in Table 1.
On D 1 a necropsy was performed on Sheep 1 and representative tissues were sampled and preserved in 10 % buffered formalin for histological examination.The tissues were routinely processed and stained with haematoxylin and eosin (HE).
A fluorescence polarisation immunoassay (FPIA) (Abbott TDx Analyzer, Abbott Laboratories, Illinois) using the Digoxin II reagent pack (Abbott Laboratories) was performed on extracts of plant material (bulbs and leaves) obtained from Keetmanshoop and Beaufort West.

Botanical identification
Plants collected at both Keetmanshoop and Beaufort West were identified as Ornithogalum toxicarium (Fig. 1).This is a new species of Ornithogalum subgenus Urophyllon (Hyacinthaceae) that has only recently been described 1 .Colloquially, plants of this genus are known as chinkerinchees.
Sheep 2 exhibited open-mouth breathing, with an extended head and neck, following the stress of dosing with activated charcoal on D 1.The most prominent clinical signs on D 2 were forced abdominal breathing, groaning, tachycardia and sternal recumbency.On D 3, although still very weak, the sheep became ambulatory, had a slightly improved appetite and weak ruminal movements returned.By D 11 the animal was fully recovered.

Pathology
Necropsy examination of Sheep 1 revealed mild, multifocal pulmonary emphysema and atelectasis; mild congestion of the rumen mucosa near the rumenoreticular opening and mild oedema of the abomasal folds; mild oedema and multiple petechial haemorrhages in the mucosa of the anterior 1.5 m of the small intestine and semi-fluid faecal material.Histological lesions comprised degeneration of scattered myocardial fibres; acute interstitial pneumonia and mild brain oedema.

Fluorescence polarisation immunoassay
The assay revealed cross-reactivity with digoxin antibodies in half of the plant parts assayed, thus indicating the possible presence of a cardiac glycoside or a cardiac glycoside-like substance, which could be involved in the intoxication (Table 2).

DISCUSSION
Ornithogalum toxicarium induced an atypical poisoning in small stock referred to as krimpsiekte or 'kwylbek' krimpsiekte.In South Africa there are several highly toxic Ornithogalum species of which O. thyrsoides, O. conicum, O. saundersiae, O. prasinum and O. ornithogaloides are economically important 10,11 .These species frequently cause severe, persistent diarrhoea in livestock.In O. nanodes poisoning only occasional mild to moderate diarrhoea was reported 2 .Diarrhoea is also not a feature of Crassulaceaeinduced krimpsiekte 3,4,9,10 .The only previously known neurological effect to be caused by the toxic Ornithogalum species is blindness in cattle 10,11 .
The clinical signs observed during the laboratory trial are consistent with acute cardiac glycoside intoxication (i.e.dyspnoea, tachycardia, AV-dissociation, ruminal stasis and mucoid diarrhoea) 10,11 .Similarities with experimentally induced krimpsiekte, such as irregular, shallow breathing, tachypnoea, recumbency, paresis and standing with head hanging low, were also noticed 3,4 .The severe respiratory distress, grunting, groaning and ruminal stasis observed in the sheep during the current dosing trial were consistent with the clinical signs observed during the dosing trial conducted by Bamhare 2 .
The necropsy performed on Sheep 1 revealed mild oedema and multiple, diffuse petechiae in the mucosa of the proximal 1.5 m of the small intestine.The proximal small intestinal mucosa of ruminants that have died of cardiac glycoside poisoning often shows a diffuse or patchy congestion.One of the sheep dosed with O. nanodes plant material also exhibited congestion and haemorrhages of the duodenum and upper third of the small intestine 2 .
In 'kwylbek' krimpsiekte salivation is conspicuous.Excessive salivation has also been reported with krimpsiekte and was ascribed to clonic spasms of the muscles of mastication and deglutition.Half-chewed balls of hay sometimes occluded the pharyngeal passage 7 .
The FPIA has been developed to monitor human patients on digoxin therapy (Abbott Laboratories).Although the assay uses digoxin antibodies, cross-reactivity is sufficient to detect exposure of stock to certain bufadienolide-containing plants (R A Schultz, unpubl.data).It has also been used to detect cardiac glycosides in plant material and to confirm a history suggestive of ingestion of cardiac glycosides in humans 5 .The positive assay in some of the O. toxicarium plant parts suggests the presence of a cardiac glycoside in this Ornithogalum species.
The toxicity of the cholestane or cholestene glycosides in ruminants has not yet been evaluated, but isolation of cardiac glycosides from O. toxicarium could explain the krimpsiekte syndrome.In a preliminary investigation a toxic substance was isolated, guided by guinea-pig bioassay, but nuclear magnetic resonance (NMR) analysis showed that it was not a cardiac glycoside.A low yield and impurities prevented specific identification of the compound, which could have been a cholestane glycoside (M Bode, Toxicology Division, Onderstepoort Veterinary Institute, pers.comm., 1999).
The identification of this species as O. nanodes as reported by Bamhare 2 is probably incorrect, as it can easily be confused with O. toxicarium.The 2 species are superficially similar in having longnecked bulbs and filiform leaves, but they can be placed in different subgenera on account of their floral morphology.The differences between O. nanodes and O. toxicarium are summarised in Table 3
a Müllerb Obermeyer A A 1978